My Opinion (as a HUUUUUUUUGE fan of this particular Apple product and its potential)...
Use just about the very same strategy they are using with original video content. Allocate a good block of cash to promote

TV gaming, build/license an Apple-branded controller, offer the Apple-branded games with controller bundle for a subsidized (by big block of cash) price (or perhaps MAX out on the aggressive by duplicating the video-service rumor of "free"- imagine all

TV 4 & 5 owners getting a package from Apple with a game controller inside and a voucher for some of these new

TV games. Immediately, all of the millions of

TV 4 & 5s
already in homes would become legit game machines). "Persuade" devs with existing games already on

TV and not yet (but on iDevices) to support the controller at the launch of this bundle.
Start bundling at least ONE controller in the box with

TV (sell a second at a price to recoup the cost loss on the first free one), and "steal" from the PSX and Xbox example by including a "game" gift card/voucher for a few free game downloads so that new buyers can try out gaming on

TV.
If Apple just can't bring itself to make a controller, partner with one who will, much like Apple has partnered with entities like Harmon Kardon for Apple-influenced speakers. Then bundle a voucher for a free Apple+Partner game controller plus a few app store games with each

TV.
Use some of the block of cash to commission at least
some exclusives only for
TV... just like the original video content will be exclusive to Apple devices.
The block of cash will entice developers as only cash can. The implied partnership with Apple will also be a heavy draw. An annual gaming event- maybe just a dedicated segment at WWDC- could formally highlight a variety of impressive games on Apple hardware (probably EXCLUSIVELY on Apple hardware for a period of time). The hype, rumors and buildup around this will fire up thinking about

TV as a gaming device too. The momentum alone will likely inspire fence sitter devs to (re)consider building other games to be in-store when this rolls out.
Little can imply the "Wow!" of Metal advancements like impressive gaming demos. I can't get that excited about being able to send a text message .003% faster than last year, but show me some wow gaming graphics and new hardware always looks more impressive (and necessary, even if only by the idea that new hardware will run this game as good as it can run?).
And dedicate some visible talent to this initiative (NOT by adding this onto one of the existing player's plates so it's just "one more thing" for an Eddy or similar to juggle)... including staking out space at major game dev events around the world to illustrate that Apple is now in the "game to win."
Apple commissioned bundles of (updated) top 5 "iOS games of the year" from the past decade to revive some big-screen interest in old favorites that were once most popular? Personally, I still have much retro love for very old oldies-but-goodies circa 1980s arcade games. Retro iOS games (can they be tagged "retro" in <10 years) are probably still near & dear to iDevice owner's hearts. Slightly updated versions to run on the biggest screen in the house via

TV would scratch this itch. And those games are largely ALREADY coded, maybe looking for some new life.
And flip flop on the Steam decision. If that was about money- as I heavily suspect it was- work with Steam to cut Apple in for Steam purchases through- or used with-

TV. Personally, I think the whole concept of being able to use PC power elsewhere in the house to power games on an

TV seems too good of a concept to NOT push through in spite of how many nickels can be squeezed out of it. What a great way to get the MAJORS on

TV almost overnight... and perhaps spur on some upgraded Mac sales to boot.
Bigger picture? If Apple can finally opt to actually get in this game and seriously focus on it (which may seem to be a gigantic IF based on Apple's historical lack of interest), acquire a Nintendo or similar? It's not like finding cash for such a purchase would be a huge hurdle. A Nintendo-type acquisition could BUY the dedicated focus & gaming-talent/experience much like the video billion is buying professionals that know how to make good original video.

TV has such incredible potential in many ways (beyond just this one). I wish Apple would toss what is relatively "chump change" at it with some dedicated talent focused on treating

TV like IT is iPhone.